Air filter and fan devices are used in order to ensure in vehicle ventilation systems that the air to be conditioned in the vehicle heating, ventilation, and air conditioning system (HVAC) is mechanically pre-cleaned as far as possible before the air is conditioned thermally. Different types of devices are known from prior art.
In previous applications, the air filter was often arranged in the cowl area in the engine compartment. Therefore, in recirculation mode, air drawn from the passenger compartment was not included in filtering. Particularly disadvantageous of this solution is the fact that to an increasing extent, fouling of the evaporator takes place and hence, due to the deposits developing on the evaporator and heating heat exchanger, increased odor nuisance appears. Also, particles entrained by the air flow can mechanically affect the heat exchangers by abrasion.
In present vehicle ventilation systems, an air filter is typically arranged in front of the fan. This version of arrangement of the air filter in front of the impeller is shown in FIG. 5 representing the state of the art.
As distinct from the version described above, here also the recirculated air is filtered, but this embodiment is disadvantageous in that the overall dimensions of these systems are too large.
Positioning the air filter immediately in front of the impeller results in limited utilization of the total filter surface area while also the pressure losses rise, because the major part of the drawn in air is aspirated in the region above the impeller opening through the air filter, whereas only little air flows over the border regions. Moreover, the constant height of the filter prevents the installation space from being utilized optimally.
Positioning the filter behind the fan cancels, however, the protection of the impeller from large dirt particles so that the impeller may be damaged. In order to avoid these disadvantages, protective grids are typically disposed in front of the impeller, resulting in additional expenditure.